Responder Files

Responder 9.2 makes typed SSE and NDJSON complete incremental response contracts, from per-item runtime validation through OpenAPI and generated streaming clients.

Highlights

• @api.sse and @api.ndjson infer item contracts from sync or async iterator return annotations, with explicit model overrides when needed.
• Every yielded item is validated and serialized with Pydantic while preserving backpressure, cancellation cleanup, SSE heartbeats, and Last-Event-ID.
• responder.SSE[T] provides typed data and standard SSE metadata.
• OpenAPI describes stream media types and item schemas, and generated Python, JavaScript, TypeScript, Ruby, and PHP clients consume streams lazily.
• Immediately available first-item contract failures return HTTP 500 before headers are sent; later failures are logged and terminate the stream without emitting invalid data.

Full changelog